U.S. patent application number 16/528905 was filed with the patent office on 2020-02-13 for chemically amplified resist composition and patterning process.
This patent application is currently assigned to Shin-Etsu Chemical Co., Ltd.. The applicant listed for this patent is Shin-Etsu Chemical Co., Ltd.. Invention is credited to Jun Hatakeyama, Masaki Ohashi.
Application Number | 20200050104 16/528905 |
Document ID | / |
Family ID | 69407002 |
Filed Date | 2020-02-13 |
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United States Patent
Application |
20200050104 |
Kind Code |
A1 |
Hatakeyama; Jun ; et
al. |
February 13, 2020 |
CHEMICALLY AMPLIFIED RESIST COMPOSITION AND PATTERNING PROCESS
Abstract
A chemically amplified resist composition comprising a quencher
containing an ammonium salt of an iodized or brominated aromatic
ring-bearing carboxylic acid, and an acid generator exhibits a
sensitizing effect and an acid diffusion suppressing effect and
forms a pattern having improved resolution, LWR and CDU.
Inventors: |
Hatakeyama; Jun;
(Joetsu-shi, JP) ; Ohashi; Masaki; (Joetsu-shi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Shin-Etsu Chemical Co., Ltd. |
Tokyo |
|
JP |
|
|
Assignee: |
Shin-Etsu Chemical Co.,
Ltd.
Tokyo
JP
|
Family ID: |
69407002 |
Appl. No.: |
16/528905 |
Filed: |
August 1, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03F 7/0045 20130101;
G03F 7/027 20130101; G03F 7/0392 20130101; G03F 7/0382 20130101;
G03F 7/0397 20130101 |
International
Class: |
G03F 7/004 20060101
G03F007/004; G03F 7/027 20060101 G03F007/027; G03F 7/039 20060101
G03F007/039; G03F 7/038 20060101 G03F007/038 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 9, 2018 |
JP |
2018-150146 |
Claims
1. A chemically amplified resist composition comprising a quencher
containing an ammonium salt of a carboxylic acid having an iodized
or brominated aromatic ring, and an acid generator.
2. The resist composition of claim 1 wherein the ammonium salt has
the formula (1) or (2): ##STR00254## wherein R.sup.1 is hydrogen,
hydroxyl, fluorine, chlorine, amino, nitro, or cyano group, or a
C.sub.1-C.sub.6 alkyl, C.sub.1-C.sub.6 alkoxy, C.sub.2-C.sub.6
acyloxy or C.sub.1-C.sub.6 alkylsulfonyloxy group, which may be
substituted with halogen, or --NR.sup.1A--C(.dbd.O)--R.sup.1B or
--NR.sup.1A--C(.dbd.O)--O--R.sup.1B, wherein R.sup.1A is hydrogen
or a C.sub.1-C.sub.6 alkyl group, R.sup.1B is a C.sub.1-C.sub.6
alkyl or C.sub.2-C.sub.8 alkenyl group, R.sup.2 to R.sup.11 are
each independently hydrogen or a C.sub.1-C.sub.24 monovalent
hydrocarbon group which may contain a halogen, hydroxyl, carboxyl,
ether bond, ester bond, thioether bond, thioester bond, thionoester
bond, dithioester bond, amino, nitro, sulfone or ferrocenyl moiety,
at least two of R.sup.2 to R.sup.5 may bond together to form a
ring, R.sup.2 and R.sup.3, taken together, may form
.dbd.C(R.sup.2A)(R.sup.3A), wherein R.sup.2A and R.sup.3A are each
independently hydrogen or a C.sub.1-C.sub.16 monovalent hydrocarbon
group, R.sup.2A and R.sup.4 may bond together to form a ring with
the carbon and nitrogen atoms to which they are attached, the ring
optionally containing a double bond, oxygen, sulfur or nitrogen
atom, R.sup.12 is a C.sub.2-C.sub.12 alkanediyl group which may
contain an ether bond, ester bond, carboxy moiety, thioester bond,
thionoester bond or dithioester bond, X.sup.1 is iodine or bromine,
and may be the same or different when m is at least 2, L.sup.1 is a
single bond or a C.sub.1-C.sub.20 divalent linking group which may
contain an ether bond, carbonyl moiety, ester bond, amide bond,
sultone ring, lactam ring, carbonate bond, halogen, hydroxyl or
carboxyl moiety, m and n each are an integer, meeting
1.ltoreq.m.ltoreq.5, 0.ltoreq.n.ltoreq.3, and
1.ltoreq.m+n.ltoreq.5.
3. The resist composition of claim 1 wherein the acid generator is
capable of generating sulfonic acid, imidic acid or methide
acid.
4. The resist composition of claim 1, further comprising a base
polymer.
5. The resist composition of claim 4 wherein the base polymer
comprises recurring units of at least one type selected from
recurring units having the formulae (f1) to (f3): ##STR00255##
wherein R.sup.A is each independently hydrogen or methyl, Z.sup.1
is a single bond, phenylene, --O--Z.sup.11--,
--C(.dbd.O)--O--Z.sup.11--, or --C(.dbd.O)--NH--Z.sup.11--,
Z.sup.11 is a C.sub.1-C.sub.6 alkanediyl group, C.sub.2-C.sub.6
alkenediyl group or phenylene group, which may contain a carbonyl
moiety, ester bond, ether bond or hydroxyl moiety, Z.sup.2 is a
single bond, --Z.sup.21--C(.dbd.O)--O--, --Z.sup.21--O--, or
--Z.sup.21--O--C(.dbd.O)--, Z.sup.21 is a C.sub.1-C.sub.12
alkanediyl group which may contain a carbonyl moiety, ester bond or
ether bond, Z.sup.3 is a single bond, methylene, ethylene,
phenylene, fluorinated phenylene, --O--Z.sup.31--,
--C(.dbd.O)--O--Z.sup.31--, or --C(.dbd.O)--NH--Z.sup.31--,
Z.sup.31 is a C.sub.1-C.sub.6 alkanediyl group, C.sub.2-C.sub.6
alkenediyl group, phenylene, fluorinated phenylene, or
trifluoromethyl-substituted phenylene group, which may contain a
carbonyl moiety, ester bond, ether bond or hydroxyl moiety,
R.sup.31 to R.sup.38 are each independently a C.sub.1-C.sub.20
monovalent hydrocarbon group which may contain a heteroatom, any
two of R.sup.33, R.sup.34 and R.sup.35 or any two of R.sup.36,
R.sup.37 and R.sup.38 may bond together to form a ring with the
sulfur atom to which they are attached, A.sup.1 is hydrogen or
trifluoromethyl, and M.sup.- is a non-nucleophilic counter ion.
6. The resist composition of claim 1 wherein the acid generator
also functions as a base polymer.
7. The resist composition of claim 6 wherein the acid generator is
a polymer comprising recurring units of at least one type selected
from recurring units having the formulae (f1) to (f3): ##STR00256##
wherein R.sup.A is each independently hydrogen or methyl, Z.sup.1
is a single bond, phenylene, --O--Z.sup.11--,
--C(.dbd.O)--O--Z.sup.11--, or --C(.dbd.O)--NH--Z.sup.11--,
Z.sup.11 is a C.sub.1-C.sub.6 alkanediyl group, C.sub.2-C.sub.6
alkenediyl group or phenylene group, which may contain a carbonyl
moiety, ester bond, ether bond or hydroxyl moiety, Z.sup.2 is a
single bond, --Z.sup.21--C(.dbd.O)--O--, --Z.sup.21O--, or
--Z.sup.21--O--C(.dbd.O)--, Z.sup.21 is a C.sub.1-C.sub.12
alkanediyl group which may contain a carbonyl moiety, ester bond or
ether bond, Z.sup.3 is a single bond, methylene, ethylene,
phenylene, fluorinated phenylene, --O--Z.sup.31--,
--C(.dbd.O)--Z.sup.31--, or --C(.dbd.O)--NH--Z.sup.31--, Z.sup.31
is a C.sub.1-C.sub.6 alkanediyl group, C.sub.2-C.sub.6 alkenediyl
group, phenylene, fluorinated phenylene, or
trifluoromethyl-substituted phenylene group, which may contain a
carbonyl moiety, ester bond, ether bond or hydroxyl moiety,
R.sup.31 to R.sup.38 are each independently a C.sub.1-C.sub.20
monovalent hydrocarbon group which may contain a heteroatom, any
two of R.sup.33, R.sup.34 and R.sup.35 or any two of R.sup.36,
R.sup.37 and R.sup.38 may bond together to form a ring with the
sulfur atom to which they are attached, A.sup.1 is hydrogen or
trifluoromethyl, and M.sup.- is a non-nucleophilic counter ion.
8. The resist composition of claim 4 wherein the base polymer
comprises recurring units having the formula (a1) or recurring
units having the formula (a2): ##STR00257## wherein R.sup.A is each
independently hydrogen or methyl, R.sup.21 and R.sup.22 are each
independently an acid labile group, Y.sup.1 is a single bond,
phenylene, naphthylene, or a C.sub.1-C.sub.12 linking group
containing an ester bond and/or lactone ring, and Y.sup.2 is a
single bond or ester bond.
9. The resist composition of claim 8 which is a chemically
amplified positive resist composition.
10. The resist composition of claim 4 wherein the base polymer is
an acid labile group-free polymer.
11. The resist composition of claim 10 which is a chemically
amplified negative resist composition.
12. The resist composition of claim 1, further comprising an
organic solvent.
13. The resist composition of claim 1, further comprising a
surfactant.
14. A pattern forming process comprising the steps of coating the
resist composition of claim 1 onto a substrate, baking, exposing
the resulting resist film to high-energy radiation, and developing
the exposed resist film in a developer.
15. The process of claim 14 wherein the high-energy radiation is
ArF excimer laser of wavelength 193 nm or KrF excimer laser of
wavelength 248 nm.
16. The process of claim 14 wherein the high-energy radiation is EB
or EUV of wavelength 3 to 15 nm.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This non-provisional application claims priority under 35
U.S.C. .sctn. 119(a) on Patent Application No. 2018-150146 filed in
Japan on Aug. 9, 2018, the entire contents of which are hereby
incorporated by reference.
TECHNICAL FIELD
[0002] This invention relates to a chemically amplified resist
composition comprising a quencher containing an ammonium salt of a
carboxylic acid having an iodized or brominated aromatic ring, and
an acid generator, and a patterning process using the same.
BACKGROUND ART
[0003] To meet the demand for higher integration density and
operating speed of LSIs, the effort to reduce the pattern rule is
in rapid progress. The wide-spreading flash memory market and the
demand for increased storage capacities drive forward the
miniaturization technology. As the advanced miniaturization
technology, manufacturing of microelectronic devices at the 65-nm
node by the ArF lithography has been implemented in a mass scale.
Manufacturing of 45-nm node devices by the next generation ArF
immersion lithography is approaching to the verge of high-volume
application. The candidates for the next generation 32-nm node
include ultra-high NA lens immersion lithography using a liquid
having a higher refractive index than water in combination with a
high refractive index lens and a high refractive index resist film,
EUV lithography of 13.5 nm wavelength, and double patterning
version of the ArF lithography, on which active research efforts
have been made.
[0004] The exposure system for mask manufacturing made a transition
from the laser beam exposure system to the EB exposure system to
increase the accuracy of line width. Since a further size reduction
becomes possible by increasing the accelerating voltage of the
electron gun in the EB exposure system, the accelerating voltage
increased from 10 kV to 30 kV and reached 50 kV in the current
mainstream system, with a voltage of 100 kV being under
investigation.
[0005] As the pattern feature size is reduced, approaching to the
diffraction limit of light, light contrast lowers. In the case of
positive resist film, a lowering of light contrast leads to
reductions of resolution and focus margin of hole and trench
patterns.
[0006] As the pattern feature size is reduced, the edge roughness
(LWR) of line patterns and the critical dimension uniformity (CDU)
of hole patterns are regarded significant. It is pointed out that
these factors are affected by the segregation or agglomeration of a
base polymer and acid generator and the diffusion of generated
acid. There is a tendency that as the resist film becomes thinner,
LWR becomes greater. A film thickness reduction to comply with the
progress of size reduction causes a degradation of LWR, which
becomes a serious problem.
[0007] The EUV lithography resist must meet high sensitivity, high
resolution and low LWR at the same time. As the acid diffusion
distance is reduced, LWR is reduced, but sensitivity becomes lower.
For example, as the PEB temperature is lowered, the outcome is a
reduced LWR, but a lower sensitivity. As the amount of quencher
added is increased, the outcome is a reduced LWR, but a lower
sensitivity. It is necessary to overcome the tradeoff relation
between sensitivity and LWR. It would be desirable to have a resist
material having a high sensitivity and resolution as well as
improved LWR and CDU.
[0008] Patent Document 1 proposes a quencher of iodonium
carboxylate type having a carboxylate ion bonded to an iodonium
cation. Patent Documents 2 and 3 propose the use of hypervalent
iodine compounds as the quencher. Since iodine has a large atomic
weight, quenchers in the form of iodized compounds are fully
effective for suppressing acid diffusion.
[0009] Patent Document 4 discloses a resist material having an
iodized benzoic acid or iodized phenol added thereto, which exerts
a sensitizing effect due to the strong absorption of iodine
atoms.
CITATION LIST
[0010] Patent Document 1: JP 5852490 (U.S. Pat. No. 9,176,379)
[0011] Patent Document 2: JP-A 2015-180928 (U.S. Pat. No.
9,563,123)
[0012] Patent Document 3: JP-A 2015-172746 (U.S. Pat. No.
9,448,475)
[0013] Patent Document 4: JP-A 2013-83957
SUMMARY OF INVENTION
[0014] As the wavelength of light becomes shorter, the energy
density thereof becomes higher and hence, the number of photons
generated upon exposure becomes smaller. A variation in photon
number causes variations in LWR and CDU. As the exposure dose
increases, the number of photons increases, leading to a less
variation of photon number. Thus there is a tradeoff relationship
between sensitivity and resolution, LWR and CDU. In particular, the
EUV lithography resist materials have the tendency that a lower
sensitivity leads to better LWR and CDU.
[0015] An increase in acid diffusion also causes degradation of
resolution, LWR and CDU. This is because acid diffusion not only
causes image blur, but also proceeds non-uniformly in a resist
film. For suppressing acid diffusion, it is effective to lower the
PEB temperature, to use a bulky acid which is least diffusive, or
to increase the amount of quencher added. However, any of these
means for reducing acid diffusion results in a lowering of
sensitivity. Either the means for reducing photon variation or the
means for reducing acid diffusion variation leads to a lowering of
resist sensitivity.
[0016] An object of the invention is to provide a chemically
amplified resist composition which exerts a high sensitizing effect
and an acid diffusion suppressing effect and has improved
resolution, LWR and CDU, and a pattern forming process using the
same.
[0017] A significant increase of acid generation efficiency and a
significant suppression of acid diffusion must be achieved before
the tradeoff relationship between sensitivity and resolution, LWR
and CDU can be overcome.
[0018] Iodine is substantially absorptive to EUV of wavelength 13.5
nm and EB because of its large atomic weight, and releases many
secondary electrons upon exposure because of many electron orbits
in its molecule. The secondary electrons thus released provide
energy transfer to an acid generator, achieving a high sensitizing
effect.
[0019] The inventors have found that when an ammonium salt of a
carboxylic acid having an iodized or brominated aromatic ring is
added as the quencher to a chemically amplified resist composition
comprising an acid generator, the resulting resist composition
forms a resist film which exerts a high sensitizing effect and an
acid diffusion suppressing effect, experiences no film thickness
loss after development, and has a high sensitivity, minimized LWR
and improved CDU.
[0020] In one aspect, the invention provides a chemically amplified
resist composition comprising a quencher containing an ammonium
salt of a carboxylic acid having an iodized or brominated aromatic
ring, and an acid generator.
[0021] In a preferred embodiment, the ammonium salt has the formula
(1) or (2).
##STR00001##
Herein R.sup.1 is hydrogen, hydroxyl, fluorine, chlorine, amino,
nitro, or cyano group, or a C.sub.1-C.sub.6 alkyl, C.sub.1-C.sub.6
alkoxy, C.sub.2-C.sub.6 acyloxy or C.sub.1-C.sub.6 alkylsulfonyloxy
group, which may be substituted with halogen, or
--NR.sup.1A--C(.dbd.O)--R.sup.1B or
--NR.sup.1A--C(.dbd.O)--O--R.sup.1B, wherein R.sup.1A is hydrogen
or a C.sub.1-C.sub.6 alkyl group, R.sup.1B is a C.sub.1-C.sub.6
alkyl or C.sub.2-C.sub.8 alkenyl group. R.sup.2 to R.sup.11 are
each independently hydrogen or a C.sub.1-C.sub.24 monovalent
hydrocarbon group which may contain a halogen, hydroxyl, carboxyl,
ether bond, ester bond, thioether bond, thioester bond, thionoester
bond, dithioester bond, amino, nitro, sulfone or ferrocenyl moiety,
at least two of R.sup.2 to R.sup.5 may bond together to form a
ring, R.sup.2 and R.sup.3, taken together, may form
C(R.sup.2A)(R.sup.3A), wherein R.sup.2A and R.sup.3A are each
independently hydrogen or a C.sub.1-C.sub.16 monovalent hydrocarbon
group, R.sup.2A and R.sup.4 may bond together to form a ring with
the carbon and nitrogen atoms to which they are attached, the ring
optionally containing a double bond, oxygen, sulfur or nitrogen
atom. R.sup.12 is a C.sub.2-C.sub.12 alkanediyl group which may
contain an ether bond, ester bond, carboxy moiety, thioester bond,
thionoester bond or dithioester bond. X.sup.1 is iodine or bromine,
and may be the same or different when m is at least 2. L.sup.1 is a
single bond or a C.sub.1-C.sub.20 divalent linking group which may
contain an ether bond, carbonyl moiety, ester bond, amide bond,
sultone ring, lactam ring, carbonate bond, halogen, hydroxyl or
carboxyl moiety, m and n each are an integer, meeting
1.ltoreq.m.ltoreq.5, 0.ltoreq.n.ltoreq.3, and
1.ltoreq.m+n.ltoreq.5.
[0022] In a preferred embodiment, the acid generator is capable of
generating sulfonic acid, imidic acid or methide acid.
[0023] The resist composition may further comprise a base polymer,
preferably a base polymer comprising recurring units of at least
one type selected from recurring units having the formulae (f1) to
(f3).
##STR00002##
Herein R.sup.A is each independently hydrogen or methyl. Z.sup.1 is
a single bond, phenylene, --O--Z.sup.11--,
--C(.dbd.O)--O--Z.sup.11--, or --C(.dbd.O)--NH--Z.sup.11--,
Z.sup.11 is a C.sub.1-C.sub.6 alkanediyl group, C.sub.2-C.sub.6
alkenediyl group or phenylene group, which may contain a carbonyl
moiety, ester bond, ether bond or hydroxyl moiety. Z.sup.2 is a
single bond, --Z.sup.21--C(.dbd.O)--O--, --Z.sup.21--O--, or
--Z.sup.21--O--C(.dbd.O)--, Z.sup.21 is a C.sub.1-C.sub.12
alkanediyl group which may contain a carbonyl moiety, ester bond or
ether bond. Z.sup.3 is a single bond, methylene, ethylene,
phenylene, fluorinated phenylene, --O--Z.sup.31--,
--C(.dbd.O)--O--Z.sup.31--, or --C(.dbd.O)--NH--Z.sup.31--,
Z.sup.31 is a C.sub.1-C.sub.6 alkanediyl group, C.sub.2-C.sub.6
alkenediyl group, phenylene, fluorinated phenylene, or
trifluoromethyl-substituted phenylene group, which may contain a
carbonyl moiety, ester bond, ether bond or hydroxyl moiety.
R.sup.31 to R.sup.38 are each independently a C.sub.1-C.sub.20
monovalent hydrocarbon group which may contain a heteroatom, any
two of R.sup.33, R.sup.34 and R.sup.35 or any two of R.sup.36,
R.sup.37 and R.sup.38 may bond together to form a ring with the
sulfur atom to which they are attached. A.sup.1 is hydrogen or
trifluoromethyl. M.sup.- is a non-nucleophilic counter ion.
[0024] In a preferred embodiment, the acid generator also functions
as a base polymer. More preferably, the acid generator is a polymer
comprising recurring units of at least one type selected from
recurring units having the formulae (f1) to (f3).
##STR00003##
Herein R.sup.A is each independently hydrogen or methyl. Z.sup.1 is
a single bond, phenylene, --O--Z.sup.11--,
--C(.dbd.O)--O--Z.sup.11--, or --C(.dbd.O)--NH--Z.sup.11--,
Z.sup.11 is a C.sub.1-C.sub.6 alkanediyl group, C.sub.2-C.sub.6
alkenediyl group or phenylene group, which may contain a carbonyl
moiety, ester bond, ether bond or hydroxyl moiety. Z.sup.2 is a
single bond, --Z.sup.21--C(.dbd.O)--O--, --Z.sup.21--O--, or
--Z.sup.21--O--C(.dbd.O)--, Z.sup.21 is a C.sub.1-C.sub.12
alkanediyl group which may contain a carbonyl moiety, ester bond or
ether bond. Z.sup.3 is a single bond, methylene, ethylene,
phenylene, fluorinated phenylene, --O--Z.sup.31--,
--C(.dbd.O)--O--Z.sup.31--, or --C(.dbd.O)--NH--Z.sup.31--,
Z.sup.31 is a C.sub.1-C.sub.6 alkanediyl group, C.sub.2-C.sub.6
alkenediyl group, phenylene, fluorinated phenylene, or
trifluoromethyl-substituted phenylene group, which may contain a
carbonyl moiety, ester bond, ether bond or hydroxyl moiety.
R.sup.31 to R.sup.38 are each independently a C.sub.1-C.sub.20
monovalent hydrocarbon group which may contain a heteroatom, any
two of R.sup.33, R.sup.34 and R.sup.35 or any two of R.sup.36,
R.sup.37 and R.sup.38 may bond together to form a ring with the
sulfur atom to which they are attached. A.sup.1 is hydrogen or
trifluoromethyl. M.sup.- is a non-nucleophilic counter ion.
[0025] In a preferred embodiment, the base polymer comprises
recurring units having the formula (a1) or recurring units having
the formula (a2).
##STR00004##
Herein R.sup.A is each independently hydrogen or methyl, R.sup.21
and R.sup.22 are each independently an acid labile group, Y.sup.1
is a single bond, phenylene, naphthylene, or a C.sub.1-C.sub.12
linking group containing an ester bond and/or lactone ring, and
Y.sup.2 is a single bond or ester bond.
[0026] In one preferred embodiment, the resist composition is a
chemically amplified positive resist composition.
[0027] In another preferred embodiment, the base polymer is an acid
labile group-free polymer. Typically the resist composition is a
chemically amplified negative resist composition.
[0028] The resist composition may further comprise an organic
solvent and/or a surfactant.
[0029] In another aspect, the invention provides a pattern forming
process comprising the steps of coating the resist composition
defined above onto a substrate, baking, exposing the resulting
resist film to high-energy radiation, and developing the exposed
resist film in a developer.
[0030] In a preferred embodiment, the high-energy radiation is ArF
excimer laser of wavelength 193 am, KrF excimer laser of wavelength
248 nm, EB or EUV of wavelength 3 to 15 nm.
Advantageous Effects of Invention
[0031] Since the ammonium salt of an iodized or brominated aromatic
ring-bearing carboxylic acid contains an iodine or bromine atom
featuring substantial light absorption, a resist film containing
the ammonium salt as a quencher exhibits a sensitizing effect due
to secondary electrons released therefrom upon exposure. Since
iodine or bromine has a large atomic weight, the resist film exerts
an acid diffusion suppressing effect. In addition, since the
ammonium salt is fully alkali soluble, a high dissolution contrast
is obtainable. Thus the resist film exhibits high resolution, high
sensitivity, minimal LWR, and improved CDU as a positive or
negative resist film subject to alkaline development or as a
negative resist film subject to organic solvent development.
DESCRIPTION OF EMBODIMENTS
[0032] As used herein, the singular forms "a," "an" and "the"
include plural referents unless the context clearly dictates
otherwise. The notation (C.sub.n-C.sub.m) means a group containing
from n to m carbon atoms per group. The term "iodized" or
"brominated" compound means an iodine or bromine-substituted
compound. In chemical formulae, Me stands for methyl, and Ac for
acetyl.
[0033] The abbreviations and acronyms have the following
meaning.
[0034] EB: electron beam
[0035] EUV: extreme ultraviolet
[0036] Mw: weight average molecular weight
[0037] Mn: number average molecular weight
[0038] Mw/Mn: molecular weight distribution or dispersity
[0039] GPC: gel permeation chromatography
[0040] PEB: post-exposure bake
[0041] PAG: photoacid generator
[0042] LWR: line width roughness
[0043] CDU: critical dimension uniformity
Chemically Amplified Resist Composition
[0044] The chemically amplified resist composition of the invention
is defined as comprising a quencher containing an ammonium salt of
a carboxylic acid having an iodized or brominated aromatic ring,
and an acid generator. The ammonium salt of carboxylic acid
undergoes ion exchange with an acid generated from the acid
generator to form another ammonium salt and release an iodized or
brominated aromatic ring-bearing carboxylic acid. The ammonium salt
of an iodized or brominated aromatic ring-bearing carboxylic acid
has an acid trapping ability and an acid diffusion suppressing
effect.
[0045] The acid diffusion suppressing effect and contrast enhancing
effect of the ammonium salt of an iodized or brominated aromatic
ring-bearing carboxylic acid are valid in both the positive or
negative pattern formation by alkaline development and the negative
pattern formation by organic solvent development.
Quencher
[0046] The quencher in the chemically amplified resist composition
contains an ammonium salt of an iodized or brominated aromatic
ring-bearing carboxylic acid. The preferred ammonium salt has the
formula (1) or (2).
##STR00005##
[0047] In formulae (1) and (2), R.sup.1 is a hydrogen atom,
hydroxyl group, fluorine atom, chlorine atom, amino group, nitro
group or cyano group, or a C.sub.1-C.sub.6 alkyl, C.sub.1-C.sub.6
alkoxy, C.sub.2-C.sub.6 acyloxy or C.sub.1-C.sub.6 alkylsulfonyloxy
group, which may be substituted with halogen, or
--NR.sup.1A--C(.dbd.O)--R.sup.1B or
--NR.sup.1A--C(.dbd.O)--O--R.sup.1B. R.sup.1A is hydrogen or a
C.sub.1-C.sub.6 alkyl group, and R.sup.1B is a C.sub.1-C.sub.6
alkyl group or C.sub.2-C.sub.8 alkenyl group.
[0048] The C.sub.1-C.sub.6 alkyl group may be straight, branched or
cyclic, and examples thereof include methyl, ethyl, n-propyl,
isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,
cyclobutyl, n-pentyl, cyclopentyl, n-hexyl, and cyclohexyl.
Examples of the alkyl moiety in the C.sub.1-C.sub.6 alkoxy,
C.sub.2-C.sub.7 acyloxy and C.sub.2-C.sub.7 alkoxycarbonyl groups
are as exemplified above for the alkyl group. Examples of the alkyl
moiety in the C.sub.1-C.sub.4 alkylsulfonyloxy group are those of 1
to 4 carbons among the examples mentioned above for the alkyl
group. The C.sub.2-C.sub.8 alkenyl group may be straight, branched
or cyclic, and examples thereof include vinyl, 1-propenyl, and
2-propenyl. Among others, R.sup.1 is preferably fluorine, chlorine,
hydroxyl, amino, C.sub.1-C.sub.3 alkyl, C.sub.1-C.sub.3 alkoxy,
C.sub.2-C.sub.4 acyloxy, --NR.sup.1A--C(.dbd.O)--R.sup.1B or
--NR.sup.1A--C(.dbd.O)--O--R.sup.1B.
[0049] R.sup.2 to R.sup.11 are each independently hydrogen or a
C.sub.1-C.sub.24 monovalent hydrocarbon group which may contain a
halogen atom, hydroxyl moiety, carboxyl moiety, ether bond, ester
bond, thioether bond, thioester bond, thionoester bond, dithioester
bond, amino moiety, nitro moiety, sulfone moiety or ferrocenyl
moiety. At least two of R.sup.2 to R.sup.5 may bond together to
form a ring, R.sup.2 and R.sup.3, taken together, may form
.dbd.C(R.sup.2A)(R.sup.3A), wherein R.sup.2A and R.sup.3A are each
independently hydrogen or a C.sub.1-C.sub.16 monovalent hydrocarbon
group, R.sup.2A and R.sup.4 may bond together to form a ring with
the carbon and nitrogen atoms to which they are attached, and the
ring may contain a double bond, oxygen, sulfur or nitrogen
atom.
[0050] The monovalent hydrocarbon group may be straight, branched
or cyclic. Examples thereof include C.sub.1-C.sub.24 alkyl groups,
C.sub.2-C.sub.24 alkenyl groups, C.sub.2-C.sub.24 alkynyl groups,
C.sub.6-C.sub.20 aryl groups, C.sub.7-C.sub.20 aralkyl groups, and
combinations thereof.
[0051] R.sup.12 is a C.sub.2-C.sub.12 alkanediyl group which may
contain an ether bond, ester bond, carboxyl moiety, thioester bond,
thionoester bond or dithioester bond. The alkanediyl group may be
straight, branched or cyclic, and examples thereof include
methylene, ethylene, propane-1,3-diyl, butane-1,4-diyl,
pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl,
octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl,
undecane-1,11-diyl, dodecane-1,12-diyl, cyclopentanediyl, and
cyclohexanediyl.
[0052] X.sup.1 is an iodine or bromine atom, and may be the same or
different when m is at least 2.
[0053] L.sup.1 is a single bond or a C.sub.1-C.sub.20 divalent
linking group which may contain an ether bond, carbonyl moiety,
ester bond, amide bond, sultone ring, lactam ring, carbonate bond,
halogen atom, hydroxyl moiety or carboxyl moiety.
[0054] The subscripts m and n each are an integer, meeting
1.ltoreq.m.ltoreq.5, 0.ltoreq.n.ltoreq.3, and
1.ltoreq.m+n.ltoreq.5, preferably 1.ltoreq.m.ltoreq.3 and
0.ltoreq.n.ltoreq.2.
[0055] Examples of the anion in the ammonium salt having fonnula
(1) or (2) are shown below, but not limited thereto.
##STR00006## ##STR00007## ##STR00008## ##STR00009## ##STR00010##
##STR00011## ##STR00012## ##STR00013## ##STR00014## ##STR00015##
##STR00016## ##STR00017## ##STR00018## ##STR00019## ##STR00020##
##STR00021## ##STR00022## ##STR00023## ##STR00024## ##STR00025##
##STR00026## ##STR00027## ##STR00028## ##STR00029##
##STR00030##
[0056] Examples of the cation in the ammonium salt having formula
(1) are shown below, but not limited thereto.
##STR00031## ##STR00032## ##STR00033## ##STR00034## ##STR00035##
##STR00036## ##STR00037## ##STR00038##
##STR00039## ##STR00040## ##STR00041## ##STR00042## ##STR00043##
##STR00044## ##STR00045## ##STR00046## ##STR00047## ##STR00048##
##STR00049## ##STR00050## ##STR00051## ##STR00052## ##STR00053##
##STR00054## ##STR00055## ##STR00056## ##STR00057## ##STR00058##
##STR00059## ##STR00060## ##STR00061## ##STR00062## ##STR00063##
##STR00064##
##STR00065## ##STR00066## ##STR00067## ##STR00068## ##STR00069##
##STR00070## ##STR00071## ##STR00072## ##STR00073##
##STR00074##
[0057] Examples of the cation in the ammonium salt having formula
(2) are shown below, but not limited thereto.
##STR00075## ##STR00076## ##STR00077##
[0058] Since the ammonium salt contains iodine or bromine in the
molecule, it has substantial EUV absorption. Upon EUV exposure, it
generates secondary electrons, followed by energy transfer to an
acid generator, leading to sensitization. This establishes a high
sensitivity and low acid diffusion, succeeding in improving both
LWR or CDU and sensitivity.
[0059] The ammonium salt may be synthesized, for example, by
neutralization reaction of an ammonium hydroxide or amine compound
with an iodized or brominated carboxylic acid.
[0060] As the cation of the ammonium salt, a quaternary ammonium
cation is preferred because the most acid diffusion suppressing
effect is exerted. When a primary, secondary or tertiary ammonium
cation is used, the acid diffusion suppressing effect may be
enhanced by changing the substituent bonded to the nitrogen atom in
the ammonium cation to a bulky structure, for example, an
optionally substituted C.sub.3-C.sub.24 monovalent hydrocarbon
group or a structure having two substituent groups bonded together
to form a ring with the nitrogen atom to which they are
attached.
[0061] While the resist composition of the invention may be
prepared by dissolving the ammonium salt and other resist
components in an organic solvent in any arbitrary order or at the
same time, the resist composition containing the desired ammonium
salt may also be prepared by adding an amine compound capable of
providing the cation of the desired ammonium salt and an iodized or
brominated carboxylic acid capable of providing the anion of the
desired ammonium salt to a solution containing other resist
components, and effecting neutralization reaction in the solution.
In this case, the amine compound and the iodized or brominated
carboxylic acid are preferably combined in such amounts that a
molar ratio of amine compound/carboxylic acid may range from 0.8 to
1.2 (i.e., 0.8.ltoreq.amine compound/carboxylic acid.ltoreq.1.2),
more preferably from 0.9 to 1.1, even more preferably from 0.95 to
1.05.
[0062] Alternatively, the resist composition containing the desired
ammonium salt may be prepared by adding a sulfonium salt having the
anion of the desired ammonium salt and an ammonium salt consisting
of the cation of the desired ammonium salt and a fluorosulfonic
acid anion to a solution containing other resist components, and
effecting cation exchange between the salts in the solution. The
fluorosulfonic acid ammonium salt may be either of addition type or
of polymer bound type (i.e., bound to the polymer main chain). In
this case, the sulfonium salt and the fluorosulfonic acid ammonium
salt are preferably combined in such amounts that a molar ratio of
sulfonium salt/ammonium salt may range from 0.8 to 1.2 (i.e.,
0.8.ltoreq.sulfonium salt/ammonium salt.ltoreq.1.2), more
preferably from 0.9 to 1.1, even more preferably from 0.95 to
1.05.
[0063] From the standpoints of sensitivity and acid diffusion
suppressing effect, the ammonium salt is preferably present in the
resist composition in an amount of 0.001 to 50 parts, more
preferably 0.01 to 20 parts by weight per 100 parts by weight of
the base polymer to be described below.
[0064] The quencher may contain a quencher other than the ammonium
salt. The other quencher is typically selected from conventional
basic compounds. Conventional basic compounds include primary,
secondary, and tertiary aliphatic amines, mixed amines, aromatic
amines, heterocyclic amines, nitrogen-containing compounds with
carboxyl group, nitrogen-containing compounds with sulfonyl group,
nitrogen-containing compounds with hydroxyl group,
nitrogen-containing compounds with hydroxyphenyl group, alcoholic
nitrogen-containing compounds, amide derivatives, imide
derivatives, and carbamate derivatives. Also included are primary,
secondary, and tertiary amine compounds, specifically amine
compounds having a hydroxyl group, ether bond, ester bond, lactone
ring, cyano group, or sulfonic acid ester bond as described in JP-A
2008-111103, paragraphs [0146]-[0164], and compounds having a
carbamate group as described in JP 3790649. Addition of a basic
compound may be effective for further suppressing the diffusion
rate of acid in the resist film or correcting the pattern
profile.
[0065] Quenchers of polymer type as described in U.S. Pat. No.
7,598,016 (JP-A 2008-239918) are also useful as the other quencher.
The polymeric quencher segregates at the resist surface after
coating and thus enhances the rectangularity of resist pattern.
When a protective film is applied as is often the case in the
immersion lithography, the polymeric quencher is also effective for
preventing a film thickness loss of resist pattern or rounding of
pattern top.
[0066] Also, an ammonium salt, sulfonium salt or iodonium salt may
be added as the other quencher. Suitable ammonium salts, sulfonium
salts and iodonium salts added as the other quencher are salts with
carboxylic acid, sulfonic acid, sulfonimide and saccharin. The
carboxylic acid used herein may or may not be fluorinated at
.alpha.-position.
[0067] The other quencher is preferably added in an amount of 0 to
5 parts, more preferably 0 to 4 parts by weight per 100 parts by
weight of the base polymer.
Acid Generator
[0068] The chemically amplified resist composition contains an acid
generator. The acid generator used herein may be either an acid
generator of addition type which is different from the ammonium
salt and components to be described later, or an acid generator of
polymer bound type which also functions as a base polymer, that is,
an acid generator-and-base polymer component.
[0069] The acid generator of addition type is typically a compound
(PAG) capable of generating an acid upon exposure to actinic ray or
radiation. Although the PAG used herein may be any compound capable
of generating an acid upon exposure to high-energy radiation, those
compounds capable of generating sulfonic acid, sulfonimide or
sulfonmethide are preferred. Suitable PAGs include sulfonium salts,
iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, and
oxime-O-sulfonate acid generators. Exemplary PAGs are described in
JP-A 2008-111103, paragraphs [0122]-[0142] (U.S. Pat. No.
7,537,880).
[0070] As the PAG, compounds having the formula (3) are also
preferably used.
##STR00078##
[0071] In formula (3), R.sup.101, R.sup.102 and R.sup.103 are each
independently a C.sub.1-C.sub.20 monovalent hydrocarbon group which
may contain a heteroatom, any two of R.sup.101, R.sup.102 and
R.sup.103 may bond together to form a ring with the sulfur atom to
which they are attached. The monovalent hydrocarbon group may be
straight, branched or cyclic, and examples thereof include
C.sub.1-C.sub.12 alkyl groups, C.sub.6-C.sub.12 aryl groups, and
C.sub.7-C.sub.20 aralkyl groups. Also included are substituted
forms of the foregoing groups in which some or all of the hydrogen
atoms are substituted by C.sub.1-C.sub.10 alkyl, halogen,
trifluoromethyl, cyano, nitro, hydroxyl, mercapto, C.sub.1-C.sub.10
alkoxy, C.sub.2-C.sub.10 alkoxycarbonyl, or C.sub.2-C.sub.10
acyloxy moieties, or some carbon is substituted by a carbonyl
moiety, ether bond or ester bond.
[0072] Examples of the cation in the sulfonium salt having formula
(3) are shown below, but not limited thereto.
##STR00079## ##STR00080## ##STR00081## ##STR00082## ##STR00083##
##STR00084## ##STR00085## ##STR00086## ##STR00087## ##STR00088##
##STR00089## ##STR00090## ##STR00091## ##STR00092## ##STR00093##
##STR00094## ##STR00095## ##STR00096## ##STR00097## ##STR00098##
##STR00099## ##STR00100## ##STR00101## ##STR00102## ##STR00103##
##STR00104## ##STR00105## ##STR00106## ##STR00107## ##STR00108##
##STR00109## ##STR00110##
[0073] In formula (3), X.sup.- is an anion selected from the
formulae (3A) to (3D).
##STR00111##
[0074] In formula (3A), R.sup.fa is fluorine or a C.sub.1-C.sub.40
straight, branched or cyclic monovalent hydrocarbon group which may
contain a heteroatom.
[0075] Of the anions of formula (3A), a structure having formula
(3A') is preferred.
##STR00112##
[0076] In formula (3A'), R.sup.104 is hydrogen or trifluoromethyl,
preferably trifluoromethyl. R.sup.105 is a C.sub.1-C.sub.38
straight, branched or cyclic monovalent hydrocarbon group which may
contain a heteroatom. Suitable heteroatoms include oxygen,
nitrogen, sulfur and halogen, with oxygen being preferred. Of the
monovalent hydrocarbon groups, those of 6 to 30 carbon atoms are
preferred because a high resolution is available in fine pattern
formation. Suitable monovalent hydrocarbon groups include methyl,
ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl,
pentyl, neopentyl, cyclopentyl, hexyl, cyclohexyl, 3-cyclohexenyl,
heptyl, 2-ethylhexyl, nonyl, undecyl, tridecyl, pentadecyl,
heptadecyl, 1-damantyl, 2-adamantyl, 1-adamantylmethyl, norbornyl,
norbornylmethyl, tricyclodecanyl, tetracyclododecanyl,
tetracyclododecanylmethyl, dicyclohexylmethyl, icosanyl, allyl,
benzyl, diphenylmethyl, tetrahydrofuryl, methoxymethyl,
ethoxymethyl, methylthiomethyl, acetamidomethyl, trifluoroethyl,
(2-methoxyethoxy)methyl, acetoxymethyl, 2-arboxy-yclohexyl,
2-oxopropyl, 4-oxo-1-adamantyl, and 3-oxocyclohexyl. Also included
are the foregoing groups in which some hydrogen is replaced by a
radical containing a heteroatom such as oxygen, sulfur, nitrogen or
halogen, or in which some carbon is replaced by a radical
containing a heteroatom such as oxygen, sulfur or nitrogen, so that
the group may contain a hydroxyl, cyano, carbonyl, ether, ester,
sulfonic acid ester, carbonate, lactone ring, sultone ring,
carboxylic acid anhydride or haloalkyl radical.
[0077] With respect to the synthesis of the sulfonium salt having
an anion of formula (3A'), reference is made to JP-A 2007-145797,
JP-A 2008-106045, JP-A 2009-007327, and JP-A 2009-258695. Also
useful are the sulfonium salts described in JP-A 2010-215608, JP-A
2012-041320, JP-A 2012-106986, and JP-A 2012-153644.
[0078] Examples of the anion having formula (3A) are shown below,
but not limited thereto.
##STR00113## ##STR00114## ##STR00115## ##STR00116##
[0079] In formula (3B), R.sup.fb1 and R.sup.fb2 are each
independently fluorine or a C.sub.1-C.sub.40 straight, branched or
cyclic monovalent hydrocarbon group which may contain a
heteroatom.
[0080] Suitable monovalent hydrocarbon groups are as exemplified
above for R.sup.105. Preferably R.sup.fb1 and R.sup.fb2 each are
fluorine or a straight C.sub.1-C.sub.4 fluorinated alkyl group. A
pair of R.sup.fb1 and R.sup.fb2 may bond together to form a ring
with the linkage (--CF.sub.2--SO.sub.2--N--SO.sub.2--CF.sub.2--) to
which they are attached, and preferably the pair is a fluorinated
ethylene or fluorinated propylene group to form a ring
structure.
[0081] In formula (3C), R.sup.fc1, R.sup.fc2 and R.sup.fc3 are each
independently fluorine or a C.sub.1-C.sub.40 straight, branched or
cyclic monovalent hydrocarbon group which may contain a heteroatom.
Suitable monovalent hydrocarbon groups are as exemplified above for
R.sup.105. Preferably R.sup.fc1, R.sup.fc2 and R.sup.fc3 each are
fluorine or a straight C.sub.1-C.sub.4 fluorinated alkyl group. A
pair of R.sup.fc1 and R.sup.fc2 may bond together to form a ring
with the linkage
(--CF.sub.2--SO.sub.2--C.sup.---SO.sub.2--CF.sub.2--) to which they
are attached, and preferably the pair is a fluorinated ethylene or
fluorinated propylene group to form a ring structure.
[0082] In formula (3D), R.sup.fd is a C.sub.1-C.sub.40 straight,
branched or cyclic monovalent hydrocarbon group which may contain a
heteroatom. Suitable monovalent hydrocarbon groups are as
exemplified above for R.sup.105.
[0083] With respect to the synthesis of the sulfonium salt having
an anion of formula (3D), reference is made to JP-A 2010-215608 and
JP-A 2014-133723.
[0084] Examples of the anion having formula (3D) are shown below,
but not limited thereto.
##STR00117## ##STR00118##
[0085] The compound having the anion of formula (3D) has a
sufficient acid strength to cleave acid labile groups in the base
polymer because it is free of fluorine at .alpha.-position of sulfo
group, but has two trifluoromethyl groups at .beta.-position. Thus
the compound is a useful PAG.
[0086] Also compounds having the formula (4) are useful as the
PAG.
##STR00119##
[0087] In formula (4), R.sup.201 and R.sup.202 are each
independently a C.sub.1-C.sub.30 straight, branched or cyclic
monovalent hydrocarbon group which may contain a heteroatom.
R.sup.203 is a C.sub.1-C.sub.30 straight, branched or cyclic
divalent hydrocarbon group which may contain a heteroatom.
[0088] Any two of R.sup.201, R.sup.202 and R.sup.203 may bond
together to form a ring with the sulfur atom to which they are
attached. L.sup.A is a single bond, ether bond or a straight,
branched or cyclic C.sub.1-C.sub.20 divalent hydrocarbon group
which may contain a heteroatom. X.sup.A, X.sup.B, X.sup.C and
X.sup.D are each independently hydrogen, fluorine or
trifluoromethyl, with the proviso that at least one of X.sup.A,
X.sup.B, X.sup.C and X.sup.D is fluorine or trifluoromethyl, and k
is an integer of 0 to 3.
[0089] Suitable monovalent hydrocarbon groups include methyl,
ethyl, propyl, isopropyl, n-butyl, s-butyl, t-butyl, n-pentyl,
t-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, cyclopentyl,
cyclohexyl, 2-ethylhexyl, cyclopentylmethyl, cyclopentylethyl,
cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl,
cyclohexylbutyl, norbornyl, oxanorbornyl,
tricyclo[5.2.1.0.sup.2,6]decanyl, adamantyl, phenyl, naphthyl and
anthracenyl. Also included are the foregoing groups in which some
hydrogen is replaced by a radical containing a heteroatom such as
oxygen, sulfur, nitrogen or halogen, or in which some carbon is
replaced by a radical containing a heteroatom such as oxygen,
sulfur or nitrogen, so that the group may contain a hydroxyl,
cyano, carbonyl, ether, ester, sulfonic acid ester, carbonate,
lactone ring, sultone ring, carboxylic acid anhydride or haloalkyl
radical.
[0090] Suitable divalent hydrocarbon groups include linear alkane
diyl groups such as methylene, ethylene, propane-1,3-diyl;
butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl,
heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl,
decane-1,10-diyl, undecane-1,11-diyl, dodecane-1,12-diyl,
tridecane-1,13-diyl, tetradecane-1,14-diyl, pentadecane-1,15-diyl,
hexadecane-1,16-diyl, heptadecane-1,17-diyl; saturated cyclic
divalent hydrocarbon groups such as cyclopentanediyl,
cyclohexanediyl, norboranediyl, and adamantanediyl; and unsaturated
cyclic divalent hydrocarbon groups such as phenylene and
naphthylene. Also included are the foregoing groups in which some
hydrogen is replaced by an alkyl group such as methyl, ethyl,
propyl, n-butyl or t-butyl, or in which some hydrogen is replaced
by a radical containing a heteroatom such as oxygen, sulfur,
nitrogen or halogen, or in which some carbon is replaced by a
radical containing a heteroatom such as oxygen, sulfur or nitrogen,
so that the group may contain a hydroxyl, cyano, carbonyl, ether,
ester, sulfonic acid ester, carbonate, lactone ring, sultone ring,
carboxylic acid anhydride or haloalkyl radical. Suitable
heteroatoms include oxygen, nitrogen, sulfur and halogen, with
oxygen being preferred.
[0091] Of the PAGs having formula (4), those having formula (4')
are preferred.
##STR00120##
[0092] In formula (4'), L.sup.A is as defined above. R is hydrogen
or trifluoromethyl, preferably trifluoromethyl. R.sup.301,
R.sup.302 and R.sup.303 are each independently hydrogen or a
C.sub.1-C.sub.20 straight, branched or cyclic monovalent
hydrocarbon group which may contain a heteroatom. Suitable
monovalent hydrocarbon groups are as exemplified above for
R.sup.105. The subscripts x and y each are an integer of 0 to 5,
and z is an integer of 0 to 4.
[0093] Examples of the PAG having formula (4) are shown below, but
not limited thereto. Herein R is as defined above.
##STR00121## ##STR00122## ##STR00123## ##STR00124## ##STR00125##
##STR00126##
[0094] Of the foregoing PAGs, those compounds having an anion of
formula (3A') or (3D) are especially preferred because of reduced
acid diffusion and high solubility in resist solvent, and those
compounds having an anion of formula (4') are especially preferred
because of minimized acid diffusion.
[0095] Also a sulfonium or iodonium salt having an iodized or
brominated aromatic ring-bearing anion may be used as the PAG.
Suitable are sulfonium and iodonium salts having the formulae (5-1)
and (5-2).
##STR00127##
[0096] In formulae (5-1) and (5-2), X.sup.2 is iodine or bromine,
and may be the same or different when q is 2 or more.
[0097] L.sup.2 is a single bond, ether bond, ester bond; or a
C.sub.1-C.sub.6 alkanediyl group which may contain an ether bond or
ester bond. The alkanediyl group may be straight, branched or
cyclic.
[0098] R.sup.401 is a hydroxyl group, carboxyl group, fluorine,
chlorine, bromine, amino group, or a C.sub.1-C.sub.20 alkyl,
C.sub.1-C.sub.20 alkoxy, C.sub.2-C.sub.20 alkoxycarbonyl,
C.sub.2-C.sub.20 acyloxy or C.sub.1-C.sub.20 alkylsulfonyloxy
group, which may contain fluorine, chlorine, bromine, hydroxyl,
amino or C.sub.1-C.sub.10 alkoxy moiety, or
--NR.sup.401A--C(.dbd.O)--R.sup.401B or
--NR.sup.401A--C(.dbd.O)--O--R.sup.401B, wherein R.sup.401A is
hydrogen, or a C.sub.1-C.sub.6 alkyl group which may contain
halogen, hydroxyl, C.sub.1-C.sub.6 alkoxy, C.sub.2-C.sub.6 acyl or
C.sub.2-C.sub.6 acyloxy moiety, R.sup.401B is a C.sub.1-C.sub.16
alkyl, C.sub.2-C.sub.16 alkenyl or C.sub.6-C.sub.12 aryl group,
which may contain halogen, hydroxyl, C.sub.1-C.sub.6 alkoxy,
C.sub.2-C.sub.6 acyl or C.sub.2-C.sub.6 acyloxy moiety. The
foregoing alkyl, alkoxy, alkoxycarbonyl, acyloxy, acyl and alkenyl
groups may be straight, branched or cyclic. When r is 2 or more,
groups R.sup.401 may be the same or different. Of these, R.sup.401
is preferably hydroxyl, --NR.sup.4011A--C(.dbd.O)--R.sup.401B,
NR.sup.401A--C(.dbd.O)--O--R.sup.401B, fluorine, chlorine, bromine,
methyl or methoxy.
[0099] R.sup.402 is a single bond or a C.sub.1-C.sub.20 divalent
linking group when p=1, or a C.sub.1-C.sub.20 tri- or tetravalent
linking group when p=2 or 3, the linking group optionally
containing an oxygen, sulfur or nitrogen atom.
[0100] Rf.sup.1 to R.sup.f are each independently hydrogen,
fluorine or trifluoromethyl, at least one of Rf.sup.1 to Rf.sup.4
is fluorine or trifluoromethyl, or Rf.sup.1 and Rf.sup.2, taken
together, may form a carbonyl group. Preferably, both Rf.sup.3 and
Rf.sup.4 are fluorine.
[0101] R.sup.403, R.sup.404, R.sup.405, R.sup.406 and R.sup.407 are
each independently a C.sub.1-C.sub.20 monovalent hydrocarbon group
which may contain a heteroatom. Any two of R.sup.403, R.sup.404 and
R.sup.405 may bond together to form a ring with the sulfur atom to
which they are attached. The monovalent hydrocarbon group may be
straight, branched or cyclic, and examples thereof include
C.sub.1-C.sub.12 alkyl, C.sub.2-C.sub.12 alkenyl, C.sub.2-C.sub.12
alkynyl, C.sub.6-C.sub.20 aryl, and C.sub.7-C.sub.12 aralkyl
groups. In these groups, some or all of the hydrogen atoms may be
substituted by hydroxyl, carboxyl, halogen, cyano, amide, nitro,
mercapto, sultone, sulfone, or sulfonium salt-containing moieties,
and some carbon may be replaced by an ether bond, ester bond,
carbonyl moiety, carbonate moiety or sulfonic acid ester bond.
[0102] In formulae (3-1) and (3-2), p is an integer of 1 to 3, q is
an integer of 1 to 5, and r is an integer of 0 to 3, and
1.ltoreq.q+r.ltoreq.5. Preferably, q is an integer of 1 to 3, more
preferably 2 or 3, and r is an integer of 0 to 2.
[0103] Examples of the cation in the sulfonium salt having formula
(5-1) include those exemplified above as the cation in the
sulfonium salt having formula (3). Examples of the cation in the
iodonium salt having formula (5-2) are shown below, but not limited
thereto.
##STR00128## ##STR00129## ##STR00130##
[0104] Examples of the anion in the onium salts having formulae
(5-1) and (5-2) are shown below, but not limited thereto. Herein
X.sup.1 is as defined above.
##STR00131## ##STR00132## ##STR00133## ##STR00134## ##STR00135##
##STR00136## ##STR00137## ##STR00138## ##STR00139## ##STR00140##
##STR00141## ##STR00142## ##STR00143## ##STR00144## ##STR00145##
##STR00146## ##STR00147## ##STR00148## ##STR00149## ##STR00150##
##STR00151## ##STR00152## ##STR00153## ##STR00154## ##STR00155##
##STR00156## ##STR00157##
##STR00158## ##STR00159## ##STR00160## ##STR00161## ##STR00162##
##STR00163## ##STR00164## ##STR00165## ##STR00166## ##STR00167##
##STR00168## ##STR00169## ##STR00170## ##STR00171## ##STR00172##
##STR00173## ##STR00174## ##STR00175## ##STR00176## ##STR00177##
##STR00178## ##STR00179## ##STR00180## ##STR00181## ##STR00182##
##STR00183## ##STR00184## ##STR00185## ##STR00186## ##STR00187##
##STR00188## ##STR00189## ##STR00190## ##STR00191## ##STR00192##
##STR00193## ##STR00194## ##STR00195## ##STR00196## ##STR00197##
##STR00198## ##STR00199## ##STR00200## ##STR00201##
[0105] An appropriate amount of the acid generator of addition type
is 0.1 to 50 parts, more preferably 1 to 40 parts by weight per 100
parts by weight of the base polymer.
[0106] In case the acid generator is an acid generator-and-base
polymer, this acid generator is a polymer, preferably comprising
recurring units derived from a compound capable of generating an
acid in response to actinic light or radiation. In this case, the
acid generator is preferably a base polymer to be described below,
specifically comprising recurring units (f) as essential unit.
Base Polymer
[0107] Where the resist composition is of positive tone, the base
polymer comprises recurring units containing an acid labile group,
preferably recurring units having the formula (a1) or recurring
units having the formula (a2). These units are simply referred to
as recurring units (a1) and (a2).
##STR00202##
[0108] Herein R.sup.A is each independently hydrogen or methyl.
R.sup.21 and R.sup.22 each are an acid labile group. Y.sup.1 is a
single bond, phenylene or naphthylene group, or C.sub.1-C.sub.12
linking group containing at least one moiety selected from ester
bond and lactone ring. Y.sup.2 is a single bond or ester bond. When
the base polymer contains both recurring units (a1) and (a2),
R.sup.21 and R.sup.22 may be the same or different.
[0109] Examples of the monomer from which the recurring units (a1)
are derived are shown below, but not limited thereto. R.sup.A and
R.sup.21 are as defined above.
##STR00203## ##STR00204##
[0110] Examples of the monomer from which the recurring units (a2)
are derived are shown below, but not limited thereto. R.sup.A and
R.sup.22 are as defined above.
##STR00205##
[0111] The acid labile groups represented by R.sup.21 and R.sup.22
in formulae (a1) and (a2) may be selected from a variety of such
groups, for example, those groups descried in JP-A 2013-080033
(U.S. Pat. No. 8,574,817) and JP-A 2013-083821 (U.S. Pat. No.
8,846,303).
[0112] Typical of the acid labile group are groups of the following
formulae (AL-1) to (AL-3).
##STR00206##
[0113] In formulae (AL-1) and (AL-2), R.sup.L1 and R.sup.L2 are
each independently a C.sub.1-C.sub.40 monovalent hydrocarbon group
which may contain a heteroatom such as oxygen, sulfur, nitrogen or
fluorine. The monovalent hydrocarbon groups may be straight,
branched or cyclic while C.sub.1-C.sub.40 alkyl groups are
preferred, and C.sub.1-C.sub.20 alkyl groups are more preferred. In
formula (AL-1), "a" is an integer of 0 to 10, preferably 1 to
5.
[0114] In formula (AL-2), R.sup.L3 and R.sup.L4 are each
independently hydrogen or a C.sub.1-C.sub.20 monovalent hydrocarbon
group which may contain a heteroatom such as oxygen, sulfur,
nitrogen or fluorine. The monovalent hydrocarbon groups may be
straight, branched or cyclic while C.sub.1-C.sub.20 alkyl groups
are preferred. Any two of R.sup.L2, R.sup.L3 and R.sup.L4 may bond
together to form a ring, typically alicyclic, with the carbon atom
or carbon and oxygen atoms to which they are attached, the ring
containing 3 to 20 carbon atoms, preferably 4 to 16 carbon
atoms.
[0115] In formula (AL-3), R.sup.L5, R.sup.L6 and R.sup.L7 are each
independently a C.sub.1-C.sub.20 monovalent hydrocarbon group which
may contain a heteroatom such as oxygen, sulfur, nitrogen or
fluorine. The monovalent hydrocarbon groups may be straight,
branched or cyclic while C.sub.1-C.sub.20 alkyl groups are
preferred. Any two of R.sup.L5, R.sup.L6 and R.sup.L7 may bond
together to form a ring, typically alicyclic, with the carbon atom
to which they are attached, the ring containing 3 to 20 carbon
atoms, preferably 4 to 16 carbon atoms.
[0116] The base polymer may further comprise recurring units (b)
having a phenolic hydroxyl group as an adhesive group. Examples of
suitable monomers from which recurring units (b) are derived are
given below, but not limited thereto. Herein R is as defined
above.
##STR00207##
[0117] Further, recurring units (c) having another adhesive group
selected from hydroxyl (other than the foregoing phenolic
hydroxyl), lactone ring, ether bond, ester bond, carbonyl, cyano,
and carboxyl groups may also be incorporated in the base polymer.
Examples of suitable monomers from which recurring units (c) are
derived are given below, but not limited thereto. Herein R.sup.A is
as defined above.
##STR00208## ##STR00209## ##STR00210## ##STR00211## ##STR00212##
##STR00213## ##STR00214## ##STR00215## ##STR00216## ##STR00217##
##STR00218## ##STR00219## ##STR00220## ##STR00221## ##STR00222##
##STR00223## ##STR00224##
[0118] In another preferred embodiment, the base polymer may
further comprise recurring units (d) selected from units of indene,
benzofuran, benzothiophene, acenaphthylene, chromone, coumarin, and
norbornadiene, or derivatives thereof. Suitable monomers are
exemplified below.
##STR00225##
[0119] Furthermore, recurring units (e) may be incorporated in the
base polymer, which are derived from styrene, vinylnaphthalene,
vinylanthracene, vinylpyrene, methyleneindene, vinylpyridine, and
vinylcarbazole.
[0120] In a further embodiment, recurring units (f) derived from an
onium salt having a polymerizable unsaturated bond may be
incorporated in the base polymer. Specifically, the base polymer
may comprise recurring units of at least one type selected from
formulae (f1), (f2) and (f3). These units are simply referred to as
recurring units (f1), (f2) and (f3), which may be used alone or in
combination of two or more types.
##STR00226##
[0121] In formulae (f1) to (f3), R.sup.A is independently hydrogen
or methyl. Z.sup.1 is a single bond, phenylene group,
--O--Z.sup.11--, --C(.dbd.O)--O--Z.sup.11--, or
--C(.dbd.O)--NH--Z.sup.11--, wherein Z.sup.11 is a C.sub.1-C.sub.6
alkanediyl group, C.sub.2-C.sub.6 alkenediyl group, or phenylene
group, which may contain a carbonyl, ester bond, ether bond or
hydroxyl moiety. Z.sup.2 is a single bond,
--Z.sup.21--C(.dbd.O)--O--, --Z.sup.21--O-- or
--Z.sup.21--O--C(.dbd.O)--, wherein Z.sup.21 is a C.sub.1-C.sub.12
alkanediyl group which may contain a carbonyl moiety, ester bond or
ether bond. A.sup.1 is hydrogen or trifluoromethyl. Z.sup.3 is a
single bond, methylene, ethylene, phenylene, fluorinated phenylene,
--O--Z.sup.31--, --C(.dbd.O)--O--Z.sup.31--, or
--C(.dbd.O)--NH--Z.sup.31--, wherein Z.sup.31 is a C.sub.1-C.sub.6
alkanediyl group, C.sub.2-C.sub.6 alkenediyl group, phenylene
group, fluorinated phenylene group, or trifluoromethyl-substituted
phenylene group, which may contain a carbonyl moiety, ester bond,
ether bond or hydroxyl moiety. The alkanediyl and alkenediyl groups
may be straight, branched or cyclic.
[0122] In formulae (f1) to (f3), R.sup.31 to R.sup.38 are each
independently a C.sub.1-C.sub.20 monovalent hydrocarbon group which
may contain a heteroatom. The monovalent hydrocarbon groups may be
straight, branched or cyclic, and examples thereof include
C.sub.1-C.sub.12 alkyl groups, C.sub.6-C.sub.12 aryl groups, and
C.sub.7-C.sub.20 aralkyl groups. In these groups, some or all of
the hydrogen atoms may be substituted by C.sub.1-C.sub.10 alkyl
groups, halogen, trifluoromethyl, cyano, nitro, hydroxyl, mercapto,
C.sub.1-C.sub.10 alkoxy groups, C.sub.2-C.sub.10 alkoxycarbonyl
groups, or C.sub.2-C.sub.10 acyloxy groups, and some carbon may be
replaced by a carbonyl moiety, ether bond or ester bond. Any two of
R.sup.33, R.sup.34 and R.sup.35 or any two of R.sup.36, R.sup.37
and R.sup.38 may bond together to form a ring with the sulfur atom
to which they are attached.
[0123] In formula (f1), M.sup.- is a non-nucleophilic counter ion.
Examples of the non-nucleophilic counter ion include halide ions
such as chloride and bromide ions; fluoroalkylsulfonate ions such
as triflate, 1,1,1-trifluoroethanesulfonate, and
nonafluorobutanesulfonate; arylsulfonate ions such as tosylate,
benzenesulfonate, 4-fluorobenzenesulfonate, and
1,2,3,4,5-pentafluorobenzenesulfonate; alkylsulfonate ions such as
mesylate and butanesulfonate; imide ions such as
bis(trifluoromethylsulfonyl)imide, bis(perfluoroethylsulfonyl)imide
and bis(perfluorobutylsulfonyl)imide; methide ions such as
tris(trifluoromethylsulfonyl)methide and
tris(perfluoroethylsulfonyl)methide.
[0124] Also included are sulfonate ions having fluorine substituted
at .alpha.-position as represented by the formula (K-1) and
sulfonate ions having fluorine substituted at .alpha.- and
.beta.-positions as represented by the formula (K-2).
##STR00227##
[0125] In formula (K-1), R.sup.51 is hydrogen, or a
C.sub.1-C.sub.20 alkyl group, C.sub.2-C.sub.20 alkenyl group, or
C.sub.6-C.sub.20 aryl group, which may contain an ether bond, ester
bond, carbonyl moiety, lactone ring, or fluorine atom. The alkyl
and alkenyl groups may be straight, branched or cyclic.
[0126] In formula (K-2), R.sup.52 is hydrogen, or a
C.sub.1-C.sub.30 alkyl group, C.sub.2-C.sub.20 acyl group,
C.sub.2-C.sub.20 alkenyl group, C.sub.6-C.sub.20 aryl group or
C.sub.6-C.sub.20 aryloxy group, which may contain an ether bond,
ester bond, carbonyl moiety or lactone ring. The alkyl, acyl and
alkenyl groups may be straight, branched or cyclic.
[0127] Examples of the monomer from which recurring unit (f1) is
derived are shown below, but not limited thereto. R.sup.A and
M.sup.- are as defined above.
##STR00228## ##STR00229## ##STR00230##
[0128] Examples of the monomer from which recurring unit (f2) is
derived are shown below, but not limited thereto. R.sup.A is as
defined above.
##STR00231## ##STR00232## ##STR00233## ##STR00234## ##STR00235##
##STR00236## ##STR00237## ##STR00238## ##STR00239##
[0129] Examples of the monomer from which recurring unit (f3) is
derived are shown below, but not limited thereto. R.sup.A is as
defined above.
##STR00240## ##STR00241## ##STR00242## ##STR00243##
##STR00244##
[0130] The attachment of an acid generator to the polymer main
chain is effective in restraining acid diffusion, thereby
preventing a reduction of resolution due to blur by acid diffusion.
Also LWR or CDU is improved since the acid generator is uniformly
distributed.
[0131] A base polymer containing recurring units (f) also functions
as an acid generator. In this embodiment wherein the base polymer
is integrated with the acid generator, that is, the acid generator
is bound to the base polymer, the resist composition may or may not
contain an acid generator of addition type.
[0132] The base polymer for formulating the positive resist
composition comprises recurring units (a1) or (a2) having an acid
labile group as essential component and additional recurring units
(b), (c), (d), (e), and (f) as optional components. A fraction of
units (a1), (a2), (b), (c), (d), (e), and (f) is: preferably
0.ltoreq.a1<1.0, 0.ltoreq.a2<1.0, 0<a1+a2<1.0,
0.ltoreq.b.ltoreq.0.9, 0.ltoreq.c.ltoreq.0.9,
0.ltoreq.d.ltoreq.0.8, 0.ltoreq.e.ltoreq.0.8, and
0.ltoreq.f.ltoreq.0.5; more preferably 0.ltoreq.a1.ltoreq.0.9,
0.ltoreq.a2.ltoreq.0.9, 0.1.ltoreq.a1+a2.ltoreq.0.9,
0.ltoreq.b.ltoreq.0.8, 0.ltoreq.c.ltoreq.0.8,
0.ltoreq.d.ltoreq.0.7, 0.ltoreq.e.ltoreq.0.7, and
0.ltoreq.f.ltoreq.0.4; and even more preferably
0.ltoreq.a1.ltoreq.0.8, 0.ltoreq.a2.ltoreq.0.8,
0.1.ltoreq.a1+a2.ltoreq.0.8, 0.ltoreq.b.ltoreq.0.75,
0.ltoreq.c.ltoreq.0.75, 0.ltoreq.d.ltoreq.0.6,
0.ltoreq.e.ltoreq.0.6, and 0.ltoreq.f.ltoreq.0.3. Where the base
polymer also functions as an acid generator, the fraction of
recurring unit (f) is preferably 0<f.ltoreq.0.5, more preferably
0.01.ltoreq.f.ltoreq.0.4, even more preferably
0.02.ltoreq.f.ltoreq.0.3. Notably, f=f1+f2+f3, meaning that unit
(f) is at least one of units (f1) to (f3), and
a1+a2+b+c+d+e+f=1.0.
[0133] For the base polymer for formulating the negative resist
composition, an acid labile group is not necessarily essential. The
base polymer comprises recurring units (b), and optionally
recurring units (c), (d), (e), and/or (f). A fraction of these
units is: preferably 0<b.ltoreq.1.0, 0.ltoreq.c.ltoreq.0.9,
0.ltoreq.d.ltoreq.0.8, 0.ltoreq.e.ltoreq.0.8, and
0.ltoreq.f.ltoreq.0.5; more preferably 0.2.ltoreq.b.ltoreq.1.0,
0.ltoreq.c.ltoreq.0.8, 0.ltoreq.d.ltoreq.0.7,
0.ltoreq.e.ltoreq.0.7, and 0.ltoreq.f.ltoreq.0.4; and even more
preferably 0.3.ltoreq.b.ltoreq.1.0, 0.ltoreq.c.ltoreq.0.75,
0.ltoreq.d.ltoreq.0.6, 0.ltoreq.e.ltoreq.0.6, and
0.ltoreq.f.ltoreq.0.3. Where the base polymer also functions as an
acid generator, the fraction of recurring unit (f) is preferably
0.ltoreq.f.ltoreq.0.5, more preferably 0.01.ltoreq.f.ltoreq.0.4,
even more preferably 0.02.ltoreq.f.ltoreq.0.3. Notably, f=f1+f2+f3,
meaning that unit (f) is at least one of units (f1) to (f3), and
b+c+d+e+f=1.0.
[0134] The base polymer may be synthesized by any desired methods,
for example, by dissolving one or more monomers selected from the
monomers corresponding to the foregoing recurring units in an
organic solvent, adding a radical polymerization initiator thereto,
and heating for polymerization. Examples of the organic solvent
which can be used for polymerization include toluene, benzene,
tetrahydrofuran, diethyl ether, and dioxane. Examples of the
polymerization initiator used herein include
2,2'-azobisisobutyronitrile (AIBN),
2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl
2,2-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl
peroxide. Preferably the system is heated at 50 to 80.degree. C.
for polymerization to take place. The reaction time is preferably 2
to 100 hours, more preferably 5 to 20 hours.
[0135] Where a monomer having a hydroxyl group is copolymerized,
the hydroxyl group may be replaced by an acetal group susceptible
to deprotection with acid, typically ethoxyethoxy, prior to
polymerization, and the polymerization be followed by deprotection
with weak acid and water. Alternatively, the hydroxyl group may be
replaced by an acetyl, formyl, pivaloyl or similar group prior to
polymerization, and the polymerization be followed by alkaline
hydrolysis.
[0136] When hydroxystyrene or hydroxyvinylnaphthalene is
copolymerized, an alternative method is possible. Specifically,
acetoxystyrene or acetoxyvinylnaphthalene is used instead of
hydroxystyrene or hydroxyvinylnaphthalene, and after
polymerization, the acetoxy group is deprotected by alkaline
hydrolysis, for thereby converting the polymer product to
hydroxystyrene or hydroxyvinylnaphthalene. For alkaline hydrolysis,
a base such as aqueous ammonia or triethylamine may be used.
Preferably the reaction temperature is -20.degree. C. to
100.degree. C., more preferably 0.degree. C. to 60.degree. C., and
the reaction time is 0.2 to 100 hours, more preferably 0.5 to 20
hours.
[0137] The base polymer should preferably have a weight average
molecular weight (Mw) in the range of 1,000 to 500,000, and more
preferably 2,000 to 30,000, as measured by GPC versus polystyrene
standards using tetrahydrofuran (THF) solvent. With too low a Mw,
the resist composition may become less heat resistant. A polymer
with too high a Mw may lose alkaline solubility and give rise to a
footing phenomenon after pattern formation.
[0138] If a base polymer has a wide molecular weight distribution
or dispersity (Mw/Mn), which indicates the presence of lower and
higher molecular weight polymer fractions, there is a possibility
that foreign matter is left on the pattern or the pattern profile
is degraded. The influences of molecular weight and dispersity
become stronger as the pattern rule becomes-finer. Therefore, the
base polymer should preferably have a narrow dispersity (Mw/Mn) of
1.0 to 2.0, especially 1.0 to 1.5, in order to provide a resist
composition suitable for micropatterning to a small feature
size.
[0139] It is understood that a blend of two or more polymers which
differ in compositional ratio, Mw or Mw/Mn is acceptable.
Other Components
[0140] With the foregoing components, other components such as an
organic solvent, surfactant, dissolution inhibitor, and crosslinker
may be blended in any desired combination to formulate a chemically
amplified positive or negative resist composition. This positive or
negative resist composition has a very high sensitivity in that the
dissolution rate in developer of the base polymer in exposed areas
is accelerated by catalytic reaction. In addition, the resist film
has a high dissolution contrast, resolution, exposure latitude, and
process adaptability, and provides a good pattern profile after
exposure, and minimal proximity bias because of restrained acid
diffusion. By virtue of these advantages, the composition is fully
useful in commercial application and suited as a pattern-forming
material for the fabrication of VLSIs.
[0141] Examples of the organic solvent are described in JP-A
2008-111103, paragraphs [0144]-[0145] (U.S. Pat. No. 7,537,880).
Exemplary solvents include ketones such as cyclohexanone,
cyclopentanone and methyl-2-n-pentyl ketone; alcohols such as
3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol,
and 1-ethoxy-2-propanol; ethers such as propylene glycol monomethyl
ether (PGME), ethylene glycol monomethyl ether, propylene glycol
monoethyl ether, ethylene glycol monoethyl ether, propylene glycol
dimethyl ether, and diethylene glycol dimethyl ether; esters such
as propylene glycol monomethyl ether acetate (PGMEA), propylene
glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate,
butyl acetate, methyl 3-methoxypropionate, ethyl
3-ethoxypropionate, t-butyl acetate, t-butyl propionate, and
propylene glycol mono-t-butyl ether acetate; and lactones such as
.gamma.-butyrolactone, which may be used alone or in admixture.
[0142] The organic solvent is preferably added in an amount of 100
to 10,000 parts, and more preferably 200 to 8,000 parts by weight
per 100 parts by weight of the base polymer.
[0143] Exemplary surfactants are described in JP-A 2008-111103,
paragraphs [0165]-[0166]. Inclusion of a surfactant may improve or
control the coating characteristics of the resist composition.
While the surfactant may be used alone or in admixture, it is
preferably added in an amount of 0.0001 to 10 parts by weight per
100 parts by weight of the base polymer.
[0144] In the case of positive resist compositions, inclusion of a
dissolution inhibitor may lead to an increased difference in
dissolution rate between exposed and unexposed areas and a further
improvement in resolution. The dissolution inhibitor which can be
used herein is a compound having at least two phenolic hydroxyl
groups on the molecule, in which an average of from 0 to 100 mol %
of all the hydrogen atoms on the phenolic hydroxyl groups are
replaced by acid labile groups or a compound having at least one
carboxyl group on the molecule, in which an average of 50 to 100
mol % of all the hydrogen atoms on the carboxyl groups are replaced
by acid labile groups, both the compounds having a molecular weight
of 100 to 1,000, and preferably 150 to 800. Typical are bisphenol
A, trisphenol, phenolphthalein, cresol novolac,
naphthalenecarboxylic acid, adamantanecarboxylic acid, and cholic
acid derivatives in which the hydrogen atom on the hydroxyl or
carboxyl group is replaced by an acid labile group, as described in
U.S. Pat. No. 7,771,914 (JP-A 2008-122932, paragraphs
[0155]-[0178]).
[0145] In the positive resist composition, the dissolution
inhibitor is preferably added in an amount of 0 to 50 parts, more
preferably 5 to 40 parts by weight per.sup.100 parts by weight of
the base polymer. The dissolution inhibitor may be used alone or in
admixture.
[0146] Where the inventive resist composition is of negative tone,
a negative pattern may be obtained by adding a crosslinker to the
composition for reducing the dissolution rate of the resist film in
the exposed region. Suitable crosslinkers which can be used herein
include epoxy compounds, melamine compounds, guanamine compounds,
glycoluril compounds and urea compounds having substituted thereon
at least one group selected from among methylol, alkoxymethyl and
acyloxymethyl groups, isocyanate compounds, azide compounds, and
compounds having a double bond such as an alkenyl ether group.
These compounds may be used as an additive or introduced into a
polymer side chain as a pendant. Hydroxy-containing compounds may
also be used as the crosslinker.
[0147] Examples of the epoxy compound include tris(2,3-epoxypropyl)
isocyanurate, trimethylolmethane triglycidyl ether,
trimethylolpropane triglycidyl ether, and tiethylolethane
triglycidyl ether. Examples of the melamine compound include
hexamethylol melamine, hexamethoxymethyl melamine, hexamethylol
melamine compounds having 1 to 6 methylol groups methoxymethylated
and mixtures thereof, hexamethoxyethyl melamine, hexaacyloxymethyl
melamine, hexamethylol melamine compounds having 1 to 6 methylol
groups acyloxymethylated and mixtures thereof. Examples of the
guanamine compound include tetramethylol guanamine,
tetramethoxymethyl guanamine, tetramethylol guanamine compounds
having 1 to 4 methylol groups methoxymethylated and mixtures
thereof, tetramethoxyethyl guanamine, tetraacyloxyguanamine,
tetramethylol guanamine compounds having 1 to 4 methylol groups
acyloxymethylated and mixtures thereof. Examples of the glycoluril
compound include tetramethylol glycoluril, tetramethoxyglycoluril,
tetramethoxymethyl glycoluril, tetramethylol glycoluril compounds
having 1 to 4 methylol groups methoxymethylated and mixtures
thereof, tetramethylol glycoluril compounds having 1 to 4 methylol
groups acyloxymethylated and mixtures thereof. Examples of the urea
compound include tetramethylol urea, tetramethoxymethyl urea,
tetramethylol urea compounds having 1 to 4 methylol groups
methoxymethylated and mixtures thereof; and tetramethoxyethyl
urea.
[0148] Suitable isocyanate compounds include tolylene diisocyanate,
diphenylmethane diisocyanate, hexamethylene diisocyanate and
cyclohexane diisocyanate. Suitable azide compounds include
1,1'-biphenyl-4,4'-bisazide, 4,4'-methylidenebisazide, and
4,4'-oxybisazide. Examples of the alkenyl ether group-containing
compound include ethylene glycol divinyl ether, triethylene glycol
divinyl ether, 1,2-propanediol divinyl ether, 1,4-butanediol
divinyl ether, tetramethylene glycol divinyl ether, neopentyl
glycol divinyl ether, trimethylol propane trivinyl ether,
hexanediol divinyl ether, 1,4-cyclohexanediol divinyl ether,
pentaerythritol trivinyl ether, pentaerythritol tetravinyl ether,
sorbitol tetravinyl ether, sorbitol pentavinyl ether, and
trimethylol propane trivinyl ether.
[0149] In the negative resist composition, the crosslinker is
preferably added in an amount of 0.1 to 50 parts, more preferably 1
to 40 parts by weight per 100 parts by weight of the base
polymer.
[0150] To the resist composition, a polymeric additive or water
repellency improver may also be added for improving the water
repellency on surface of a resist film as spin coated. The water
repellency improver may be used in the topcoatless immersion
lithography. Suitable water repellency improvers include polymers
having a fluoroalkyl group and polymers having a specific structure
with a 1,1,1,3,3,3-hexafluoro-2-propanol residue and are described
in JP-A 2007-297590 and JP-A 2008-111103, for example. The water
repellency improver to be added to the resist composition should be
soluble in the organic solvent as the developer. The water
repellency improver of specific structure with a
1,1,1,3,3,3-hexafluoro-2-propanol residue is well soluble in the
developer. A polymer having an amino group or amine salt
copolymerized as recurring units may serve as the water repellent
additive and is effective for preventing evaporation of acid during
PEB, thus preventing any hole pattern opening failure after
development. The water repellency improver may be used alone or in
admixture. An appropriate amount of the water repellency improver
is 0 to 20 parts, more preferably 0.5 to 10 parts by weight per 100
parts by weight of the base polymer.
[0151] Also, an acetylene alcohol may be blended in the resist
composition. Suitable acetylene alcohols are described in JP-A
2008-122932, paragraphs [0179]-[0182]. An appropriate amount of the
acetylene alcohol blended is 0 to 5 parts by weight per 100 parts
by weight of the base polymer.
Pattern Forming Process
[0152] The resist composition is used in the fabrication of various
integrated circuits. Pattern formation using the resist composition
may be performed by well-known lithography processes. The process
generally involves coating, prebaking, exposure, and development.
If necessary, any additional steps may be added.
[0153] For example, the resist composition is first applied onto a
substrate on which an integrated circuit is to be formed (e.g., Si,
SiO.sub.2, SiN, SiON, TiN, WSi, BPSG, SOG, or organic
antireflective coating) or a substrate on which a mask circuit is
to be formed (e.g., Cr, CrO, CrON, MoSi.sub.2, or SiO.sub.2) by a
suitable coating technique such as spin coating, roll coating, flow
coating, dipping, spraying or doctor coating. The coating is
prebaked on a hot plate at a temperature of 60 to 150.degree. C.
for 10 seconds to 30 minutes, preferably at 80 to 120.degree. C.
for 30 seconds to 20 minutes. The resulting resist film is
generally 0.01 to 2 .mu.m thick.
[0154] The resist film is then exposed to a desired pattern of
high-energy radiation such as UV, deep-UV, EB, EUV, x-ray, soft
x-ray, excimer laser light, .gamma.-ray or synchrotron radiation.
When UV, deep-UV, EUV, x-ray, soft x-ray, excimer laser light,
.gamma.-ray or synchrotron radiation is used as the high-energy
radiation, the resist film is exposed thereto through a mask having
a desired pattern in a dose of preferably about 1 to 200
mJ/cm.sup.2, more preferably about 10 to 100 mJ/cm.sup.2. When EB
is used as the high-energy radiation, the resist film is exposed
thereto through a mask having a desired pattern or directly in a
dose of preferably about 0.1 to 100 .mu.C/cm.sup.2, more preferably
about 0.5 to 50 .mu.C/cm.sup.2. It is appreciated that the
inventive resist composition is suited in micropatterning using KrF
excimer laser, ArF excimer laser, EB, EUV, x-ray, soft x-ray, 7-ray
or synchrotron radiation.
[0155] After the exposure, the resist film may be baked (PEB) on a
hot plate at 60 to 150.degree. C. for 10 seconds to 30 minutes,
preferably at 80 to 120.degree. C. for 30 seconds to 20
minutes.
[0156] After the exposure or PEB, in the case of positive resist,
the resist film is developed in a developer in the form of an
aqueous base solution for 3 seconds to 3 minutes, preferably 5
seconds to 2 minutes by conventional techniques such as dip, puddle
and spray techniques. A typical developer is a 0.1 to 10 wt %,
preferably 2 to 5 wt % aqueous solution of tetramethylammonitum
hydroxide (TMAH), tetraethylammonium hydroxide (TEAH),
tetrapropylammonium hydroxide (TPAH), or tetrabutylammonium
hydroxide (TBAH). The resist film in the exposed area is dissolved
in the developer whereas the resist film in the unexposed area is
not dissolved. In this way, the desired positive pattern is formed
on the substrate. Inversely in the case of negative resist, the
exposed area of resist film is to insolubilized and the unexposed
area is dissolved in the developer.
[0157] In an alternative embodiment, a negative pattern may be
formed via organic solvent development. The developer used herein
is preferably selected from among 2-octanone, 2-nonanone,
2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone, 3-hexanone,
diisobutyl ketone, methylcyclohexanone, acetophenone,
methylacetophenone, propyl acetate, butyl acetate, isobutyl
acetate, pentyl acetate, butenyl acetate, isopentyl acetate, propyl
formate, butyl formate, isobutyl formate, pentyl formate, isopentyl
formate, methyl valerate, methyl pentenoate, methyl crotonate,
ethyl crotonate, methyl propionate, ethyl propionate, ethyl
3-ethoxypropionate, methyl lactate, ethyl lactate, propyl lactate,
butyl lactate, isobutyl lactate, pentyl lactate, isopentyl lactate,
methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, methyl
benzoate, ethyl benzoate, phenyl acetate, benzyl acetate, methyl
phenylacetate, benzyl formate, phenylethyl formate, methyl
3-phenylpropionate, benzyl propionate, ethyl phenylacetate, and
2-phenylethyl acetate, and mixtures thereof.
[0158] At the end of development, the resist film is rinsed. As the
rinsing liquid, a solvent which is miscible with the developer and
does not dissolve the resist film is preferred. Suitable solvents
include alcohols of 3 to 10 carbon atoms, ether compounds of 8 to
12 carbon atoms, alkanes, alkenes, and alkynes of 6 to 12 carbon
atoms, and aromatic solvents. Specifically, suitable alcohols of 3
to 10 carbon atoms include n-propyl alcohol, isopropyl alcohol,
1-butyl alcohol, 2-butyl alcohol, isobutyl alcohol, t-butyl
alcohol, 1-pentanol, 2-pentanol, 3-pentanol, t-pentyl alcohol,
neopentyl alcohol, 2-methyl-1-butanol, 3-methyl-1-butanol,
3-methyl-3-pentanol, cyclopentanol, 1-hexanol, 2-hexanol,
3-hexanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol,
3,3-dimethyl-2-butanol, 2-ethyl-1-butanol, 2-methyl-1-pentanol,
2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol,
3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol,
4-methyl-2-pentanol, 4-methyl-3-pentanol, cyclohexanol, and
1-octanol. Suitable ether compounds of 8 to 12 carbon atoms include
di-n-butyl ether, diisobutyl ether, di-s-butyl ether, di-n-pentyl
ether, diisopentyl ether, di-s-pentyl ether, di-t-pentyl ether, and
di-n-hexyl ether. Suitable alkanes of 6 to 12 carbon atoms include
hexane, heptane, octane, nonane, decane, undecane, dodecane,
methylcyclopentane, dimethylcyclopentane, cyclohexane,
methylcyclohexane, dimethylcyclohexane, cycloheptane, cyclooctane,
and cyclononane. Suitable alkenes of 6 to 12 carbon atoms include
hexene, heptene, octene, cyclohexene, methylcyclohexene,
dimethylcyclohexene, cycloheptene, and cyclooctene. Suitable
alkynes of 6 to 12 carbon atoms include hexyne, heptyne, and
octyne. Suitable aromatic solvents include toluene, xylene,
ethylbenzene, isopropylbenzene, t-butylbenzene and mesitylene. The
solvents may be used alone or in admixture.
[0159] Rinsing is effective for minimizing the risks of resist
pattern collapse and defect formation. However, rinsing is not
essential. If rinsing is omitted, the amount of solvent used may be
reduced.
[0160] A hole or trench pattern after development may be shrunk by
the thermal flow, RELACS.RTM. or DSA process. A hole pattern is
shrunk by coating a shrink agent thereto, and baking such that the
shrink agent may undergo crosslinking at the resist surface as a
result of the acid catalyst diffusing from the resist layer during
bake, and the shrink agent may attach to the sidewall of the hole
pattern. The bake is preferably at a temperature of 70 to
180.degree. C., more preferably 80 to 170.degree. C., for a time of
10 to 300 seconds. The extra shrink agent is stripped and the hole
pattern is shrunk.
EXAMPLES
[0161] Examples of the invention are given below by way of
illustration and not by way of limitation. The abbreviation "pbw"
is parts by weight.
[0162] Quenchers 1 to 22, Amine compound 1, Carboxylic acid 1 used
in resist compositions have the structure shown below. Quenchers 1
to 22 were prepared by neutralization reaction of an ammonium
hydroxide or amine compound providing the cation shown below with
an iodized or brominated aromatic ring-bearing carboxylic acid
providing the anion shown below.
##STR00245## ##STR00246## ##STR00247## ##STR00248##
##STR00249##
Synthesis Example
[0163] Synthesis of Base Polymers (Polymers 1 to 3)
[0164] Base polymers were prepared by combining suitable monomers,
effecting copolymerization reaction thereof in tetrahydrouran (THF)
solvent, pouring the reaction solution into methanol for
crystallization, repeatedly washing with hexane, isolation, and
drying. The resulting polymers, designated Polymers 1 to 3, were
analyzed for composition by .sup.1H-NMR spectroscopy, and for Mw
and Mw/Mn by GPC versus polystyrene standards using THF
solvent.
##STR00250## ##STR00251##
Examples 1 to 27 and Comparative Examples 1 to 7
Preparation of Resist Compositions
[0165] Resist compositions were prepared by dissolving components
in a solvent in accordance with the recipe shown in Tables 1 to 3,
and filtering through a filter having a pore size of 0.2 .mu.m. The
solvent contained 100 ppm of surfactant FC-4430 (3M). The
components in Tables 1 to 3 are as identified below.
Base polymers: Polymers 1 to 3 of the above structural formulae
Organic Solvents:
[0166] PGMEA (propylene glycol monomethyl ether acetate)
[0167] CyH (cyclohexanone)
[0168] PGME (propylene glycol monomethyl ether)
Acid generators: PAG 1 to PAG 4 of the following structural
formulae
##STR00252##
Comparative Quenchers 1 to 5:
##STR00253##
[0169] EUV Lithography Test
[0170] Each of the resist compositions in Tables 1 to 3 was spin
coated on a silicon substrate having a 20-nm coating of
silicon-containing spin-on hard mask SHB-A940 (Shin-Etsu Chemical
Co., Ltd., silicon content 43 wt %) and prebaked on a hotplate at
105.degree. C. for 60 seconds to form a resist film of 60 nm thick.
Using an EUV scanner NXE3300 (ASML, NA 0.33, a 0.9/0.6, quadrupole
illumination), the resist film was exposed to EUV through a mask
bearing a hole pattern at a pitch 46 nm (on-wafer size) and +20%
bias. The resist film was baked (PEB) on a hotplate at the
temperature shown in Tables 1 to 3 for 60 seconds and developed in
a 2.38 wt % TMAH aqueous solution for 30 seconds to form a hole
pattern having a size of 23 nm in Examples 1 to 25, 27 and
Comparative Examples 1 to 6 or a dot pattern having a size of 23 nm
in Example 26 and Comparative Example 7.
[0171] The resist pattern was evaluated using CD-SEM (CG-5000,
Hitachi High-Technologies Corp.). The exposure dose that provides a
hole or dot pattern having a size of 23 nm is reported as
sensitivity. The size of 50 holes or dots was measured, from which
a size variation (3a) was computed and reported as CDU.
[0172] The resist composition is shown in Tables 1 to 3 together
with the sensitivity and CDU of EUV lithography.
TABLE-US-00001 TABLE 1 Acid Organic PEB Polymer generator Base
solvent temp. Sensitivity CDU (pbw) (pbw) (pbw) (pbw) (.degree. C.)
(mJ/cm.sup.2) (nm) Example 1 Polymer 1 -- Quencher 1 PGMEA (400) 80
23 2.9 (100) (7.41) CyH (2,000) PGME (100) 2 Polymer 1 -- Quencher
2 PGMEA (400) 80 25 2.7 (100) (6.31) CyH (2,000) PGME (100) 3
Polymer 1 -- Quencher 3 PGMEA (400) 80 22 2.3 (100) (8.55) CyH
(2,000) PGME (100) 4 Polymer 1 -- Quencher 4 PGMEA (400) 80 26 2.8
(100) (6.15) CyH (2,000) PGME (100) 5 Polymer 1 -- Quencher 5 PGMEA
(400) 80 22 2.8 (100) (5.00) CyH (2,000) PGME (100) 6 Polymer 1 --
Quencher 6 PGMEA (400) 80 26 2.5 (100) (7.17) CyH (2,000) PGME
(100) 7 Polymer 1 -- Quencher 7 PGMEA (400) 80 26 2.6 (100) (7.23)
CyH (2,000) PGME (100) 8 Polymer 1 -- Quencher 8 PGMEA (400) 80 25
2.8 (100) (8.29) CyH (2,000) PGME (100) 9 Polymer 1 -- Quencher 9
PGMEA (400) 80 22 2.3 (100) (6.90) CyH (2,000) PGME (100) 10
Polymer 1 -- Quencher 10 PGMEA (400) 80 24 2.5 (100) (8.99) CyH
(2,000) PGME (100) 11 Polymer 1 -- Quencher 11 PGMEA (400) 80 22
2.9 (100) (6.73) CyH (2,000) PGME (100) 12 Polymer 1 -- Quencher 12
PGMEA (400) 80 20 2.8 (100) (7.86) CyH (2,000) PGME (100) 13
Polymer 1 -- Quencher 13 PGMEA (400) 80 25 2.3 (100) (7.81) CyH
(2,000) PGME (100) 14 Polymer 1 -- Quencher 14 PGMEA (400) 80 26
2.7 (100) (6.40) CyH (2,000) PGME (100)
TABLE-US-00002 TABLE 2 Acid Organic PEB Polymer generator Base
solvent temp. Sensitivity CDU (pbw) (pbw) (pbw) (pbw) (.degree. C.)
(mJ/cm.sup.2) (nm) Example 15 Polymer 1 -- Quencher 15 PGMEA (400)
80 26 2.3 (100) (5.90) CyH (2,000) PGME (100) 16 Polymer 1 --
Quencher 16 PGMEA (400) 80 22 2.7 (100) (8.54) CyH (2,000) PGME
(100) 17 Polymer 1 -- Quencher 17 PGMEA (400) 80 28 2.7 (100)
(6.64) CyH (2,000) PGME (100) 18 Polymer 1 -- Quencher 18 PGMEA
(400) 80 22 2.8 (100) (6.31) CyH (2,000) PGME (100) 19 Polymer 1 --
Quencher 19 PGMEA (400) 80 21 2.8 (100) (6.40) CyH (2,000) PGME
(100) 20 Polymer 1 -- Quencher 20 PGMEA (400) 80 22 2.8 (100)
(6.40) CyH (2,000) PGME (100) 21 Polymer 1 -- Quencher 21 PGMEA
(400) 80 26 2.1 (100) (10.16) CyH (2,000) PGME (100) 22 Polymer 1
-- Quencher 22 PGMEA (400) 80 27 2.2 (100) (10.65) CyH (2,000) PGME
(100) 23 Polymer 1 PAG 1 Quencher 21 PGMEA (400) 80 20 2.6 (100)
(7) (10.16) CyH (2,000) PGME (100) 24 Polymer 1 PAG 3 Quencher 22
PGMEA (400) 80 18 2.4 (100) (8) (10.65) CyH (2,000) PGME (100) 25
Polymer 2 PAG 2 Quencher 1 PGMEA (2,000) 90 27 2.8 (100) (10)
(7.41) CyH (500) 26 Polymer 3 PAG 4 Quencher 1 PGMEA (2,000) 120 28
3.2 (100) (10) (7.41) CyH (500) 27 Polymer 1 -- Amine PGMEA (400)
80 28 2.3 (100) compound 1 CyH (2,000) (5.15) PGME (100) Carboxylic
acid 1 (5.00)
TABLE-US-00003 TABLE 3 Acid Organic PEB Polymer generator Base
solvent temp. Sensitivity CDU (pbw) (pbw) (pbw) (pbw) (.degree. C.)
(mJ/cm.sup.2) (nm) Comparative 1 Polymer 1 -- Comparative PGMEA
(400) 100 28 3.5 Example (100) Quencher 1 CyH (2,000) (2.50) PGME
(100) 2 Polymer 1 -- Comparative PGMEA (400) 100 28 3.2 (100)
Quencher 2 CyH (2,000) (4.42) PGME (100) 3 Polymer 1 -- Comparative
PGMEA (400) 100 24 2.9 (100) Quencher 3 CyH (2,000) (3.63) PGME
(100) Carboxylic acid 1 (5.00) 4 Polymer 1 -- Comparative PGMEA
(400) 100 28 2.8 (100) Quencher 4 CyH (2,000) (3.23) PGME (100) 5
Polymer 1 -- Comparative PGMEA (400) 100 38 3.0 (100) Quencher 5
CyH (2,000) (3.20) PGME (100) 6 Polymer 2 PAG 2 Comparative PGMEA
(2,000) 100 30 3.0 (100) (10) Quencher 1 CyH (500) (2.50) 7 Polymer
3 PAG 1 Comparative PGMEA (2,000) 120 30 4.9 (100) (10) Quencher 1
CyH (500) (2.50)
[0173] It is demonstrated in Tables 1 to 3 that resist compositions
comprising an ammonium salt of an iodized or brominated aromatic
ring-bearing carboxylic acid form patterns having a high
sensitivity, satisfactory resolution, and reduced values of
CDU.
[0174] Japanese Patent Application No. 2018-150146 is incorporated
herein by reference.
[0175] Although some preferred embodiments have been described,
many modifications and variations may be made thereto in light of
the above teachings. It is therefore to be understood that the
invention may be practiced otherwise than as specifically described
without departing from the scope of the appended claims.
* * * * *